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Add Backend wrapper for Celo functionality
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,101 @@ | ||
| package celoapi | ||
|
|
||
| import ( | ||
| "context" | ||
| "fmt" | ||
| "math/big" | ||
|
|
||
| "github.com/ethereum/go-ethereum/common" | ||
| "github.com/ethereum/go-ethereum/common/exchange" | ||
| "github.com/ethereum/go-ethereum/common/lru" | ||
| "github.com/ethereum/go-ethereum/contracts" | ||
| "github.com/ethereum/go-ethereum/internal/ethapi" | ||
| "github.com/ethereum/go-ethereum/rpc" | ||
| ) | ||
|
|
||
| func NewCeloAPIBackend(b ethapi.Backend) *CeloAPIBackend { | ||
| return &CeloAPIBackend{ | ||
| Backend: b, | ||
| exchangeRatesCache: lru.NewCache[common.Hash, common.ExchangeRates](128), | ||
| } | ||
| } | ||
|
|
||
| // CeloAPIBackend is a wrapper for the ethapi.Backend, that provides additional Celo specific | ||
| // functionality. CeloAPIBackend is mainly passed to the JSON RPC services and provides | ||
| // an easy way to make extra functionality available in the service internal methods without | ||
| // having to change their call signature significantly. | ||
| // CeloAPIBackend keeps a threadsafe LRU cache of block-hash to exchange rates for that block. | ||
| // Cache invalidation is only a problem when an already existing blocks' hash | ||
| // doesn't change, but the rates change. That shouldn't be possible, since changing the rates | ||
| // requires different transaction hashes / state and thus a different block hash. | ||
| // If the previous rates change during a reorg, the previous block hash should also change | ||
| // and with it the new block's hash. | ||
| // Stale branches cache values will get evicted eventually. | ||
| type CeloAPIBackend struct { | ||
| ethapi.Backend | ||
|
|
||
| exchangeRatesCache *lru.Cache[common.Hash, common.ExchangeRates] | ||
| } | ||
|
|
||
| func (b *CeloAPIBackend) getContractCaller(ctx context.Context, atBlock common.Hash) (*contracts.CeloBackend, error) { | ||
| state, _, err := b.Backend.StateAndHeaderByNumberOrHash( | ||
| ctx, | ||
| rpc.BlockNumberOrHashWithHash(atBlock, false), | ||
| ) | ||
| if err != nil { | ||
| return nil, fmt.Errorf("retrieve state for block hash %s: %w", atBlock.String(), err) | ||
| } | ||
| return &contracts.CeloBackend{ | ||
| ChainConfig: b.Backend.ChainConfig(), | ||
| State: state, | ||
| }, nil | ||
| } | ||
|
|
||
| func (b *CeloAPIBackend) GetFeeBalance(ctx context.Context, atBlock common.Hash, account common.Address, feeCurrency *common.Address) (*big.Int, error) { | ||
| cb, err := b.getContractCaller(ctx, atBlock) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| return contracts.GetFeeBalance(cb, account, feeCurrency), nil | ||
| } | ||
|
|
||
| func (b *CeloAPIBackend) GetExchangeRates(ctx context.Context, atBlock common.Hash) (common.ExchangeRates, error) { | ||
| cachedRates, ok := b.exchangeRatesCache.Get(atBlock) | ||
| if ok { | ||
| return cachedRates, nil | ||
| } | ||
| cb, err := b.getContractCaller(ctx, atBlock) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| er, err := contracts.GetExchangeRates(cb) | ||
| if err != nil { | ||
| return nil, fmt.Errorf("retrieve exchange rates from current state: %w", err) | ||
| } | ||
| b.exchangeRatesCache.Add(atBlock, er) | ||
| return er, nil | ||
| } | ||
|
|
||
| func (b *CeloAPIBackend) ConvertToCurrency(ctx context.Context, atBlock common.Hash, value *big.Int, fromFeeCurrency *common.Address) (*big.Int, error) { | ||
| er, err := b.GetExchangeRates(ctx, atBlock) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| currencyValue, err := exchange.ConvertGoldToCurrency(er, fromFeeCurrency, value) | ||
| if err != nil { | ||
| return nil, fmt.Errorf("could not convert to native from fee currency (%s): %w ", fromFeeCurrency, err) | ||
| } | ||
| return currencyValue, nil | ||
| } | ||
|
|
||
| func (b *CeloAPIBackend) ConvertToGold(ctx context.Context, atBlock common.Hash, value *big.Int, toFeeCurrency *common.Address) (*big.Int, error) { | ||
| er, err := b.GetExchangeRates(ctx, atBlock) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| goldValue, err := exchange.ConvertCurrencyToGold(er, value, toFeeCurrency) | ||
| if err != nil { | ||
| return nil, fmt.Errorf("could not convert from native to fee currency (%s): %w ", toFeeCurrency, err) | ||
| } | ||
| return goldValue, nil | ||
| } |
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